Graphite is the most popular anode for lithium ion batteries used in consumer electronics. However, it has poor charging rates and is unable to cycle in inexpensive, low temperature melting solvents such as propylene carbonate and tetrahydrofuran.
Hollow carbon nanospheres have the ability to charge at much higher rates and at much lower_temperatures than graphite and greatly exceed the energy storage capacity of graphite when used to support Li-alloying or Li-compound forming materials. Graphitic hollow carbon nanospheres (HCNS)_contain void spaces to alleviate local expansion of lithium alloying or compound formation, allowing for a high degree of charge/discharge reversibility (i.e. long battery life). See, e.g., U.S. Pat. Nos. 6,280,697 and 8,262,942, and U.S. Publication Nos. 2006/0278159 and 2004/0265210.
Lithium alloying metals have been applied to various rigid supports. See, e.g., Nitta et al., Particle & Particle Systems Characterization, 31(3), 317-336, 2014; McDowell et al., Advanced Materials, 25(36), 4966-4984, 2013; Besenhard et al., Journal of Power Sources, 68(1), 87-9, 1997; and Park et al., Chemical Society Reviews, 39(8), 3115-3141, 2010. However, anodes for lithium ion batteries made with such materials generally suffer from severe reversible capacity loss in subsequent cycles and thus short cycle life likely due to the very large expansion (as much as 400%) that the materials undergo upon lithiation, which causes physical degradation of the electrode, disrupting electrical conductivity paths from the current collector to the lithium alloying material rendering it inactive for reversible storage. As such, none have been successful in achieving stable performance over multiple (hundreds) charge/discharge cycles.
There is therefore a need for new materials that may be used as electrode active materials that exhibit enhanced performance, such as stability over multiple charge/discharge cycles.